Sludge biochar(BC), which was prepared by the pyrolysis of waste-activated sludge at 450℃, was applied for peroxymonosulfate(PMS) activation to construct a BC/PMS system for ciprofloxacin(CIP) degradation. The physical and chemical properties of BC were studied using scanning electron microscopy(SEM), an energy dispersive spectrometer(EDS), a Fourier transform infrared spectrometer(FTIR), X-ray diffraction(XRD), a Zeta potential analyzer, and electron paramagnetic resonance spectroscopy(EPR). The effects of BC dosage, PMS dosage, initial pH value, and inorganic anions on CIP removal in the BC/PMS system were investigated. Further, the degradation mechanism of the BC/PMS system was speculated through the free radical quenching experiment and X-ray photoelectron spectroscopy(XPS) analysis. The results showed that the CIP degradation rate was 49.09% at a BC dosage of 1.0 g·L-1, PMS of 3.0 mmol·L-1, CIP of 20 mg·L-1, and pH of 6.0 in 120 min. SO42- and NO3- had no obvious effect on the removal of CIP in the BC/PMS system, whereas HCO3- and Cl-could inhibit CIP degradation significantly. The CIP removal in the BC/PMS system was attributed to the common function of the radical pathway dominated by ·OH and SO4-· and the non-radical pathway dominated by 1O2. The CIP degradation pathway mainly included piperazine ring opening and hydroxylation reaction.
Keywords: ciprofloxacin; non-radical; peroxymonosulfate(PMS); radical; sludge biochar.